The invention relates to a method for the operation of a conveyor roller, one or more parallel sets of cross-knives and a cross-cutting apparatus comprising a sheet outfeeder, for paper or cardboard webs.
Conventional cross-cutting apparatus comprise revolving conveyor rollers for pulling a paper or carboard web from a roll and feeding it to knives which cross-cut the web into sheets, and also to a sheet outfeeder.
Also known and commonly used are so-called duplex synchronous cross-cutters which have knife drums disposed parallel to one another in tandem and provided with knives which are offset from one another, for the purpose of cross-cutting parallel strips of paper produced by longitudinal slitting.
In different states of operation, such as start-up or restarting after a shutdown of the machine due to web breakage or the like, the cross-knives are in an indefinite position with respect to the leading end of the web. Consequently, when the cross-cutting apparatus is started up, the first cut produces an excessively short sheet. This short sheet then is left on the table disposed between the cross-knives and the entrance to the sheet gate, because it is not long enough to be caught by the belts of the outfeeder. This short sheet will sooner or later be nudged along by successive sheets and may thus accidently get into the finished stack, or it may cause jam-ups and consequently machine shut-downs. In the first case complaints will be made by the industry in which the printing screens can be damaged by the short sheets. In the second case, the machine shut-downs reduce the output of the plant.